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| Titel |
CCN activation experiments with adipic acid: effect of particle phase and adipic acid coatings on soluble and insoluble particles |
| VerfasserIn |
S. S. Hings, W. C. Wrobel, E. S. Cross, D. R. Worsnop, P. Davidovits, T. B. Onasch |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 8, no. 14 ; Nr. 8, no. 14 (2008-07-15), S.3735-3748 |
| Datensatznummer |
250006281
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| Publikation (Nr.) |
 copernicus.org/acp-8-3735-2008.pdf |
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| Zusammenfassung |
| Slightly soluble atmospherically relevant organic compounds may influence
particle CCN activity and therefore cloud formation. Adipic acid is a
frequently employed surrogate for such slightly soluble organic materials.
The 11 published experimental studies on the CCN activity of adipic acid
particles are not consistent with each other nor do they, in most cases,
agree with the Köhler theory. The CCN activity of adipic acid aerosol
particles was studied over a significantly wider range of conditions than in
any previous single study. The work spans the conditions of the previous
studies and also provides alternate methods for producing "wet" (deliquesced
solution droplets) and dry adipic acid particles without the need to produce
them by atomization of aqueous solutions. The experiments suggest that the
scatter in the previously published CCN measurements is most likely due to
the difficulty of producing uncontaminated adipic acid particles by
atomization of solutions and possibly also due to uncertainties in the
calibration of the instruments. The CCN activation of the small (dm<150 nm) initially dry particles is subject to a deliquescence barrier, while
for the larger particles the activation follows the Köhler curve. Wet
adipic acid particles follow the Köhler curve over the full range of
particle diameters studied. In addition, the effect of adipic acid coatings
on the CCN activity of both soluble and insoluble particles has also been
studied. When a water-soluble core is coated by adipic acid, the
CCN-hindering effect of particle phase is eliminated. An adipic acid coating
on hydrophobic soot yields a CCN active particle. If the soot particle is
relatively small (dcore≤102 nm), the CCN activity of the coated
particles approaches the deliquescence line of adipic acid, suggesting that
the total size of the particle determines CCN activation and the soot core
acts as a scaffold. |
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